Alkoxylated alkyl amines and alkyl ether amines, particularly ethoxylated alkyl amines and ethoxylated alkyl ether amines, have many applications in industry. They can be usefully employed as adjuvants in pesticide formulations, textile processing aids, dye transfer inhibitors, acid thickeners, detergent boosters, degreasers, anti-static agents and the like.
Alkoxylated alkyl amines and alkoxylated alkyl ether amines are materials possessing the following general structures (I), respectively:
In conventional alkoxylated alkylamines, R is typically selected from a linear or branched, saturated or non-saturated alkyl group containing 8-22 carbon atoms. In alkoxylated etheramines, R corresponds to the formula:R1—O-(A)a-(B)b—(C)c,where R1 is typically a linear or branched, saturated or non-saturated alkyl group containing 8-22 carbon atoms, A and B are alkylene oxide groups containing 2-4 carbon atoms, C is alkylene group containing 3-4 carbon atoms, a, b each vary from 0-5, c is 1, X, Y, Z are alkylene oxide groups containing 2-4 carbon atoms, x is 1, and y and z each independently vary from 0-15.
As illustrated by general formula (I), the alkoxylated alkyl amines/alkoxylated alkyl ether amines possess a surfactant structure which is composed of the lipophilic groups (R or R1) and the hydrophilic groups (polyalkylene oxide). In their designed applications, the performance of alkoxylated alkyl amines and alkoxylated alkyl ether amines is dependent on a balance between the lipholicity and the hydrophilicity provided by these groups.
Even when the lipophilicity-hydrophilicity balance does exist, the performance of the alkoxylated alkyl amines/alkoxylated alkyl ether amines is not necessarily optimal. Traditionally, these materials are prepared from the base-catalyzed alkoxylation of the corresponding alkyl amines/alkyl ether amines. Such an alkoxylation reaction is actually the polymerization reaction of alkylene oxide that includes the characteristic propagation and chain transfer steps of the polymerization process. For this reason, the resulting alkoxylated alkylamine/alkyl ether amine is not a pure compound, but a mixture of many homologs.
As an example, FIG. 1 illustrates the homolog distribution of ethoxylated tallow amine prepared from the regular hydroxide-catalyzed ethoxylation of tallow amine with 5 moles of ethylene oxide. As shown in FIG. 1, the resulting ethoxylated product is not a single compound containing 5 (CH2CH2O) units as the general structure (structure I, with 2x+2y+2z=5) may suggest. Instead, the product is a mixture of several homologs whose total ethylene oxide units varies from 2 to 10. Among these homologs, only those in the middle of the distribution range have the proper liphophilic-hydrophilic balance for certain applications and, therefore, are generally preferred. For example, in the case of an ethoxylated product comprising an average ratio of 5 alkylene oxide units per molecule, homologs having a desired lipophilic-hydrophilic balance typically range from 3EO to 5EO where “EO” is an ethylene oxide unit. Homologs with shorter EO chain length (<3EO) or longer EO chain length (>5EO) are not desirable for the applications for which a 5 EO/amine ratio surfactant is ordinarily prescribed, since such longer and shorter homologs are either too lipophilic or too hydrophilic for the applications utilizing this product. For at least some applications, the presence of especially long species is particularly disadvantageous, e.g., species having an EO/amine ratio of more than about 1.5× the target ratio. Therefore, it is advantageous to develop an alkoxylation process that results in alkoxylated products with peaked distribution.
Accordingly, it is an object of the present invention to develop a process for preparation of alkoxylated ethoxylated alkyl amines and alkyl ether amines, particularly ethoxylated alkylamine and ethoxylated alkyl ether amine with peaked distribution having greatly minimized drawbacks compared to those associated with the acid-catalyzed process.
U.S. Pat. No. 4,483,941 describes the preparation of ethoxylated organic materials comprising a peaked distribution of homologs, as prepared by ethoxylation in the presence of BF3 and metal alkyls or metal alkoxides, SiF4 and metal alkyls or metal alkoxides, or mixtures of all these catalysts. The reference lists alcohols, alkyl phenols, polyols, aldehydes, ketones, amines, amides, organic acids and mercaptans as substrates that may be ethoxylated. The patent includes a long list of amines that are subject to ethoxylation, particularly including octylamine and hexadecylamine. Working examples describe ethoxylation of C12 to C14 alcohols.
East German patent DD 219,478 describes the ethoxylation of amines in the presence of Lewis acid catalysts. A number of working examples are included which embody reactions with C12 primary amine at ethylene oxide to amine ratios in the ranges of about 2, 3 and 6. At ratios of about 3 and about 6, final reaction temperatures range from 179° to 207° C.
U.S. Pat. No. 6,376,721 describes the alkoxylation of alcohols, amines, mercaptans and amides in the presence of a rare earth triflimide catalyst to obtain a peaked distribution of homologs. Working examples describe the ethoxylation of dodecanol.
Hreczuch & Szymanowski, Recent Res. In Oil Chem., 2 (1998), pp. 63-76 describes ethoxylation in the presence of a calcium-based W7™ catalyst to obtain narrow range distributed ethoxylated alcohols. Fig. 6 of this reference also reflects the ethoxylation of tallowamine in the presence of this catalyst and provides a curve illustrating distribution of homologs. The reference explains that in conventional ethoxylation of an alcohol, the reaction rate constants increase for successive stages of oxyethylene, which results in a wide distribution of homologs and typically a significant fraction of unreacted alcohol. It is further explained that the kinetics of alkylamine ethoxylation are different from the kinetics of alcohol ethoxylation.
WO 02/38269 describes a catalyst comprising Ca sulfate, Ca acetate, low molecular weight Ca alcoholate and a crystalline phase in the form of organic Ca and sulfur compounds as a catalyst in the ethoxylation of alcohols to obtain a narrow distribution of homologs, and the use of such catalyst in the ethoxylation of organic substrates.
For a number of important commercial and industrial applications, it is desirable to provide alkoxylated alkyl(ether)amines that impart improved functional properties to formulations in which they are incorporated.
Among the particular applications in which alkoxylated alkylamine and alkoxylated etheramine surfactants have been used is herbicidal formulations, such as aqueous liquid glyphosate formulations comprising a salt of glyphosate, wherein they may serve to increase the efficacy of the herbicide in controlling or destroying unwanted vegetation.
N-phosphonomethylglycine, otherwise known as glyphosate, is well known in the art as an effective post-emergent foliar applied herbicide. Glyphosate is an organic compound that at neutral PH, contains three acidic protonatable groups, and in its acid form is relatively insoluble in water. Glyphosate is, therefore, normally formulated and applied as a water-soluble salt. Although monobasic, dibasic and tribasic salts of glyphosate can be made, it has generally been preferred to formulate and apply glyphosate, in the form of a monobasic salt, for example as a mono-(organic ammonium) salt such as the mono(isopropylamine), often abbreviated to IPA, salt, or as either monobasic or dibasic ammonium salt.
When the terms “ammonium”, “monoammonium” and “diammonium” are used herein to refer to salts of glyphosate, these terms apply strictly to inorganic ammonium, i.e., NH4+, unless the context demands otherwise. Glyphosate rates and concentrations given herein, even where the glyphosate is present as a salt or salts, are expressed as acid equivalent (a.e.) unless the context demands otherwise.
For many applications, glyphosate salts generally require the presence of a suitable surfactant for best herbicidal performance. The surfactant may be provided in the concentrate formulation, or it may be added by the end user to the diluted spray solution. The choice of surfactant can be very important since there are wide variations among surfactants in their ability to enhance the herbicidal efficacy of glyphosate for particular applications.
Use of a highly concentrated aqueous formulation of glyphosate in the form of a salt made with the inorganic base ammonia and potassium is advantageous. Ammonia and potassium are low in cost, readily available, low in molecular weight, relatively soluble in water. Additionally, they are natural nutrients for the growth of plants and other organisms. Both potassium salts and ammonium salts have been used in substantial commercial volumes. Not all surfactants are as compatible with the potassium and ammonium salts at higher concentrations as they typically are with the isopropylamine salt, especially in concentrated aqueous liquid formulations. The use of ammonium salts of glyphosate for preparing aqueous concentrate formulations of glyphosate suitable for killing and controlling weeds and other plants has, however, been somewhat limited due to difficulties arising from chemical and physical properties thereof, lack of suitable surfactants for preparing high-loaded liquid concentrates of such salts, reduced weed control, and requirement for complex processes for preparing liquid ammonium glyphosate compositions.
Potassium salts have recently been introduced to the market and have been highly successful. However, potassium salts are not as easy to formulate as isopropylamine salts, for example. With respect to stability, especially as reflected in the cloud points of high load concentrates, the constraints on selection and concentration of surfactants in high load potassium salt solutions are generally more limiting than in the case of isopropylamine salts.
The economical preparation of high efficacy glyphosate salt solutions depends on selecting a suitable surfactant or combination of surfactants, and providing an optimal concentration of the surfactant(s), often the highest concentration(s) that can be achieved without sacrifice of stability. Ethoxylated alkylamines have proven excellent bioefficacy in enhancing the herbicidal potency of glyphosate. However, in a concentrated glyphosate formulation with sufficient loading of the useful ethoxylated alkylamines, especially in potassium and ammonium glyphosate formulations, the formulation may not be stable at elevated temperature. Above a threshold glyphosate concentration, any substantial increase in the concentration of surfactant is typically only achievable at the expense of reducing glyphosate a.e. loading (concentration of glyphosate active). Likewise, any substantial increase in glyphosate a.e. loading of these products is often achievable only at the expense of surfactant concentration and may therefore impose a constraint on formulating to a surfactant concentration that is optimal for a desired application. Generally, it is desirable to develop an stable aqueous ammonium, potassium, or mixed salts glyphosate formulation (i) having high glyphosate a.e. loading, (ii) containing an ethoxylated alkylamine surfactant, and (iii) having a high enough concentration of that surfactant to provide formulation stability and efficacy sufficient for the application for which a given formulation is prepared. There is a constant objective of providing formulations of improved herbicidal efficacy, improved storage and handling characteristics, or reduced cost, or which meet two or more of such criteria.
In this context, a C8 to C22 alkylamine substituted by reaction with two moles of alkylene oxide, i.e., a bis(hydroxyalkyl) amine has a high degree of compatibility with a glyphosate salt, but limited value as an adjuvant to enhance the efficacy of the herbicide. C8 to C22 alkylamines having longer chain alkylene oxide substituents are more effective as adjuvants but are not as compatible with concentrated aqueous solutions of glyphosate salts, and may cause the formulation to suffer from a relatively low cloud point, e.g., <35° C. For certain herbicidal applications, the optimal surfactant may typically have an average alkylene oxide to amine ratio between about 3 and about 6. But even where the surfactant possesses such an average ratio, it may contain some unavoidable fractions of <3:1 (EO to amine ratio) and >6:1 species, the presence of which can detract from either performance properties or stability of the formulation. In this case, species having a ratio of >8:1 may have a particularly adverse effect on stability. However, there are other applications where glyphosate formulations may typically include a surfactant wherein the average alkylene oxide to amine ratio is in the range of about 8 to about 12, or about 12 to about 18. Aqueous liquid concentrates comprising the latter surfactants are formulated in a manner which preserves stability despite the relatively long alkylene oxide chains, but it remains preferable to minimize the concentration of homolog species that are well above the target, e.g., in the case of a surfactant designed to have a ratio between 8 and 12, it may be preferable to minimize the fraction of homologs having an alkylene oxide/amine ratio>12:1, or in the case of a surfactant designed to have a ratio between 12 and 18, it may be preferable to minimize the fraction wherein the ratio is greater than about 20:1 or 22:1.